Thought I'd try my luck here with so many technically skilled members visiting this place. I've posted on Assembler before about an early version of Moon for PSX when the game was considered for localization. One of the main features of this earlier iteration of the game is there was another player available that ended up being cut for the final. That character's graphics still exist within the game's data along with a lot of other content that can be accessed one way or another. This leads me to assume it is still possible to play as the character, but they've just blocked it out manually somehow. My hacking skills only go as far as making cheat codes (everything on that TCRF page is all stuff I found, btw). There are points in the game where you play as different characters, so I've done simple comparison of RAM values with the PEC cheat plugin to see if some sort of RAM value exists that dictates the character you play as, but I've randomly found myself trying this again and again for the past three years and accept it's likely more complicated than that. Is there anyone here that has the know-how for this sort of thing and would be interested, or kind enough, to give this a check and see what can be found? I realize this might not be such a well-known game since it's not in English yet. If anyone would care, though, I can offer to have you as a beta tester for the English translation which I translated. Our project hacker still has a lot of bugs to figure out before we have this ready, but it's the least I can do. PM me for more details if you can help. If not, I hope you enjoy the translation when we have it done, anyway!
I'm not a PSX hacker but I'd like to share my 2 cents; if we make the assumption that the game has scripted scenario data and isn't just hardcoded from A to Z then it would follow that each character has some sort of reference in the scenario data. Finding the reference for that particular character would enable you to see if the character is indeed in the game or if it is just leftover graphics. Depending on how the scenario data is stored and structured you might have to reverse some file formats. Since you are already translating the game it sounds like you have the know-how of the games resource data. Now perhaps it would be as easy as hacking a savegame and change characters in the party. Altenatively if you find the place in the scenario data where the character was supposed to be introduced you might be able to re-integrate the characte (less likely). If you are unlucky then perhaps you would need to modify the executable, which is a whole different beast.
The hacker has the know-how, I only ever did the translation work. He's busy with lots of other projects on top of this and likely won't have time to set aside for this. Plus he's told me he doesn't feel his skills are up to par for something like this which is beyond translation hacking. Editing a savegame could be interesting, although I've got no idea how to do that myself. Looked up editing memory card data but that doesn't seem like anything I'm capable of.
Could be indeed left overs with no references anywhere. Many games tend to do stuff like that, say Resident Evil 3 with its playable Brad and Dario Rosso which can't be really used.
Well, I've gotten a couple unused text events to activate after hours of messing with PEC cheating engine. Still could use help since it hasn't yielded my main goal yet.